1. Field of the Invention
The present invention relates to a spindle unit of a machine tool having an unclamping apparatus for unclamping a tool from a tool spindle.
2. Related Art
Generally, a spindle unit of a machine tool is provided with an unclamping apparatus for arranging a draw bar for clamping and unclamping a tool to insert into a through hole of a spindle movably in an axial direction and mounting a number of belleville springs for urging a draw bar in a clamping direction and unclamping the tool clamped to the spindle. There is an unclamping apparatus of this kind having a structure in which a cylinder block having a piston driven by, for example, hydraulic pressure is fixed to a rear end wall of a spindle head on a side opposed to the tool and the cylinder block is connected with a hydraulic pipe for supplying hydraulic pressure to the cylinder block, a coolant supply pipe and an electric wiring.
Meanwhile, when maintenance of a tool spindle or replacement of the belleville spring is carried out in the spindle unit, conventionally, it is general to carry out the maintenance or the replacement by removing a total of the unclamping apparatus from the spindle head to move down on the floor and drawing the tool spindle and the draw bar from the spindle head under the state.
However, when the conventional unclamping apparatus is removed to move down on the floor, it is necessary to temporarily remove all of the hydraulic pipe, the coolant supply pipe and the electric wiring connected to the cylinder block and therefore, there poses a problem that in reattaching the unclamping apparatus the respective pipe and the wiring need to connect again to take much time and labor and operational performance is low.
Further, the above-described conventional structure poses a problem that the unclamping apparatus which is a heavy object needs to remove or attach in a state of being supported by the hand of an operator and burden of labor is enormous.